<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <script src="../jquery-3.3.1.min.js"></script>
</head>
<body>
    <p></p>
    <script>
        $(function(){
            var str = '交流方式看见你法国队八年级';
            i =  0;
            setInterval(function(){
                if (i >= str.length) {
                    i = 0;
                }
                $('p').html(show(i,str));
                i++;
            },300)

            function show(i ,str){
                var tmp =  str.substr(0,i);
                tmp += '<font color="red" size="7">' + str[i] + '</font>';
                tmp += str.substr(i+1);
                return tmp;
            }
        })
        
    </script>
</body>
</html>